U.S. patent number 5,021,045 [Application Number 07/187,230] was granted by the patent office on 1991-06-04 for retrograde venous cardioplegia catheters and methods of use and manufacture.
This patent grant is currently assigned to Research Medical, Inc.. Invention is credited to Gerald D. Buckberg, Robert J. Todd.
United States Patent |
5,021,045 |
Buckberg , et al. |
June 4, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Retrograde venous cardioplegia catheters and methods of use and
manufacture
Abstract
This invention relates to a retrograde cardioplegia catheter and
its method of use. The catheter contains two lumens, an infusion
lumen through which the cardioplegic solution flows and a pressure
sensing lumen for monitoring the fluid pressure at the point where
the solution exits the catheter. A slightly tapered, self-filling
balloon is secured to the distal end of the catheter. Also, located
at the distal end of the catheter is a soft, rounded tip to prevent
damage to the sensitive intimal tissues of the coronary sinus. A
stylet having a predetermined curve at the distal end and a handle
at the proximal end is removably located within the infusion lumen.
The predetermined curve at one end of the stylet enables the
cardioplegia catheter to be inserted quickly and accurately within
the coronary sinus through a very small incision made in the right
atrium. After the catheter is securerd in place, the stylet is
withdrawn. The catheter remains in position for the duration of the
operation in order to periodically readminister the cardioplegia
solution.
Inventors: |
Buckberg; Gerald D. (Los
Angeles, CA), Todd; Robert J. (Salt Lake City, UT) |
Assignee: |
Research Medical, Inc. (Salt
Lake City, UT)
|
Family
ID: |
22688117 |
Appl.
No.: |
07/187,230 |
Filed: |
April 28, 1988 |
Current U.S.
Class: |
604/500;
604/101.04 |
Current CPC
Class: |
A61M
25/1002 (20130101); A61M 25/1027 (20130101); A61M
25/1029 (20130101); A61M 25/0075 (20130101); A61M
2025/1086 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); A61M 25/10 (20060101); A61M
029/02 () |
Field of
Search: |
;604/51-53,96-99,102,103,264,280 ;128/344 ;606/194 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
USCI Catalog, 1967-68, p. 41. .
ACMI Catalog, 4/1972, p. 18, Pelham, N.Y. .
Gerald D. Buckberg, M.D., "Reterograde Pulmonary Venous Pressure
Measurement-Fact or Artifact?", The Journal of Thoracic and
Cardiovascular Surgery, vol. 59, No. 3, pp. 393-406, Mar. 1970.
.
Philippe Menasche, M.D. et al., "Retrograde Coronary Sinus
Perfusion: A Safe Alternative for Ensuring Cardioplegic Delivery in
Aortic Valve Surgery", The Annals of Thoracic Surgery, vol. 34, No.
6, Dec. 1982, pp. 647-658. .
Gerald D. Buckberg, M.D., "Strategies and Logic of Cardioplegic
Delivery to Prevent, Avoid, and Reverse Ischemic and Reperfusion
Damage", The Journal of Thoracic and Cardiovascular Surgery, 1987,
vol. 93, pp. 127-139. .
Donald G. Mulder et al., "Myocardial Protection During Aortic Valve
Replacement", The Annals of Thoracic Surgery, vol. 21, No. 2, Feb.
1976, pp. 123-130. .
Jorge Solorzano, M.D. et al., "Retrograde Coronary Sinus Perfusion
for Myocardial Protection During Cardiopulmonary Bypass", The
Annals of Thoracic Surgery, vol. 25, No. 3, Mar. 1978, pp. 201-208.
.
Philippe Menasche et al., "Retrograde Coronary Sinus Perfusion",
Roberts Textbook Myocardial Protection in Cardiac Surgery, printed
1987, Chapter 15, pp. 251-262. .
Charles C. Reed, Diane K. Clark, Chapter 19, "Cannulation", Chapter
23. .
"Myocardial Protection", Cardiopulmonary Perfusion, Texas Medical
Press, Inc., Houston, Tex., 1975. .
Dr. Dwight C. McGoon, "Coronary Perfusion", Journal of Thoracic and
Cardiovascular Surgery, vol. 70, No. 6, p. 1025, Dec. 1975. .
International Working Group on Coronary Sinus Interventions,
Newsletter, vol. 1, No. 3, Oct. 1987..
|
Primary Examiner: Pellegrino; Stephen C.
Assistant Examiner: Lewis; Ralph A.
Attorney, Agent or Firm: Workman, Nydegger & Jensen
Claims
What is claimed and desired to be secured by United States Letters
Patent is:
1. A catheter for performing retrograde venous cardioplegia by
delivering a cardioplegic solution into the coronary sinus of the
heart, the catheter comprising:
a flexible, dual lumen cannula of a size capable of insertion into
the coronary sinus of the heart, said cannula having an infusion
lumen and a sensing lumen;
a balloon attached to the cannula periphery near the distal end of
the cannula, thereby forming a chamber between the balloon and the
cannula;
at least one balloon aperture in the infusion lumen positioned such
that the infusion lumen is in communication with the chamber formed
by the balloon and the cannula through the at least one balloon
aperture, the aggregate of said balloon apertures having a total
cross-sectional area which is greater than the cross-sectional area
of the infusion lumen;
at least one infusion lumen outlet in the infusion lumen positioned
between the balloon and the distal end of the cannula such that,
when cardioplegic solution passes through the infusion lumen, a
portion of the cardioplegic solution enters the chamber through the
at least one balloon aperture and a portion of the cardioplegic
solution exits the infusion lumen and the cannula through the at
least one infusion lumen outlet, the aggregate of said infusion
lumen outlets having a total cross-sectional area which is in the
range of from about twenty-five percent to about seventy-five
percent of the cross-sectional area of the infusion lumen, thereby
creating a pressure within the infusion lumen which causes the
cardioplegic solution to enter the chamber through the at least one
balloon aperture in order to fill the balloon until it is turgid
and in sealing engagement with the walls of the coronary sinus;
and
at least one sensing lumen orifice in the sensing lumen located at
a point between the balloon and the distal end of the cannula which
is remote from the at least one infusion lumen outlet, said sensing
lumen orifice having a cross-sectional area greater than the
cross-sectional area of the sensing lumen.
2. A catheter as defined in claim 1, further comprising a tip
located at the distal end of the cannula such that the distal ends
of the infusion lumen and the sensing lumen are occluded at the
tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
3. A catheter as defined in claim 2, wherein the tip located at the
distal end of the cannula is constructed of a material having a
softness in the range of about 55 to about 60 durometer,
Shore-A.
4. A catheter as defined in claim 3, wherein the tip located at the
distal end of the cannula is constructed of medical grade polyvinyl
chloride.
5. A catheter as defined in claim 2, wherein the distal end of the
balloon is located back from the tip a distance in the range from
about 2 centimeters to about 6 centimeters.
6. A catheter as defined in claim 1, further comprising means
attached to the proximal end of the infusion lumen for introducing
the cardioplegic solution into and through the infusion lumen.
7. A catheter as defined in claim 6, further comprising means
attached to the proximal end of the sensing lumen for sensing the
pressure of the cardioplegic solution at the at least one sensing
lumen orifice.
8. A catheter as defined in claim 6, further comprising means for
stopping the introduction of the cardioplegic solution into the
infusion lumen when the pressure of the cardioplegic solution
exiting the at least one infusion lumen outlet exceeds a
predetermined maximum pressure.
9. A catheter as defined in claim 1, wherein the balloon is tapered
from the distal end to the proximal end of the balloon, thereby
minimizing trauma during the insertion of the cannula into the
coronary sinus and thereby encouraging the dealing engagement of
the balloon with the walls of the coronary sinus.
10. A catheter as defined in claim 9, wherein the balloon taper is
in the range from about 25.degree. to about 35.degree. measured
from the longitudinal axis of the cannula.
11. A catheter as defined in claim 1, wherein the aggregate of said
balloon apertures has a total cross-sectional area in the range of
from about 1.5 to about 5 times the cross-sectional area of the
infusion lumen.
12. A catheter as defined in claim 1, wherein the aggregate of said
balloon apertures has a total cross-sectional area in the range
from about 2 to about 3 times the cross-sectional area of the
infusion lumen.
13. A catheter as defined in claim 1, wherein the balloon, when
filled with cardioplegic solution, has a cross-sectional diameter
in the range of from about 1.6 to about 2.0 centimeters.
14. A catheter as defined in claim 1, wherein the balloon when
filled with cardioplegic solution, has a cross-sectional diameter
in the range of from about 1.7 to about 1.8 centimeters.
15. A catheter as defined in claim 1, wherein the dual lumen
cannula is constructed of a material having a softness in the range
from about 75 to about 85 durometer, Shore-A.
16. A catheter as defined in claim 15, wherein the dual lumen
cannula is constructed of medical grade polyvinyl chloride.
17. A catheter as defined in claim 1, wherein the balloon is
constructed of a material having a percent elongation greater than
about 600%.
18. A catheter as defined in claim 17, wherein the balloon is
constructed of polyurethane.
19. A catheter as defined in claim 1, further comprising a
plurality of balloon apertures in the infusion lumen.
20. A catheter as defined in claim 19, further comprising a
plurality of infusion lumen outlets in the infusion lumen.
21. A catheter as defined in claim 20, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during insertion of the cannula into the
coronary sinus and thereby encouraging the sealing engagement of
the balloon with the walls of the coronary sinus, said catheter
further comprising:
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
22. A catheter as defined in claim 19, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during insertion of the cannula into the
coronary sinus and thereby encouraging the sealing engagement of
the balloon with the walls of the coronary sinus, said catheter
further comprising:
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
23. A catheter as defined in claim 1, further comprising a
plurality of infusion lumen outlets in the infusion lumen.
24. A catheter as defined in claim 23, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during insertion of the cannula into the
coronary sinus and thereby encouraging the sealing engagement of
the balloon with the walls of the coronary sinus, said catheter
further comprising:
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
25. A catheter as defined in claim 1, wherein the cross-sectional
area of sensing lumen orifice is in the range from about 2 to about
3 times the cross-sectional area of the sensing lumen.
26. A catheter for performing retrograde venous cardioplegia by
delivering a cardioplegic solution into the coronary sinus of the
heart, the catheter comprising:
a flexible, dual lumen cannula of a size capable of insertion into
the coronary sinus of the heart, said cannula having an infusion
lumen and a sensing lumen;
a balloon attached to the cannula periphery near the distal end of
the cannula, thereby forming a chamber between the balloon and the
cannula;
at least one balloon aperture in the infusion lumen positioned such
that the infusion lumen is in communication with the chamber formed
by the balloon and the cannula through the at least one balloon
aperture;
at least one infusion lumen outlet in the infusion lumen positioned
between the balloon and the distal end of the cannula such that,
when cardioplegic solution passes through the infusion lumen, a
portion of the cardioplegic solution enters the chamber through the
at least one balloon aperture and a portion of the cardioplegic
solution exits the infusion lumen outlet, the aggregate of said
infusion lumen outlets having a total cross-sectional area which is
less than the total cross-section areas of the aggregate of said
balloon apertures in the infusion lumen, thereby creating a
pressure within the infusion lumen which causes the cardioplegic
solution to enter the chamber through the at least one balloon
aperture in order to fill the balloon until it is turgid and in
sealing engagement with the walls of the coronary sinus;
at least one sensing lumen orifice in the sensing lumen located at
a point between the balloon and the distal end of the cannula which
is remote from the at least one infusion lumen outlet, said sensing
lumen orifice having a cross-sectional area greater than the
cross-sectional area of the sensing lumen; and
a stylet removably positioned within the flexible cannula, said
stylet having a handle at the proximal end thereof and a
predetermined curve at the distal end thereof, said stylet being
constructed of a rigid material such that the stylet can be used to
position the flexible cannula in the coronary sinus with minimal
trauma to the heart tissues.
27. A catheter defined in claim 26, further comprising a tip
located at the distal end of the cannula such that the distal ends
of the infusion lumen and the sensing lumen are occluded at the
tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
28. A catheter as defined in claim 27, wherein the tip located at
the distal end of the cannula is constructed of a material having a
softness in the range of from about 55 to about 60 durometer,
Shore-A.
29. A catheter as defined in claim 28, wherein the tip located at
the distal end of the cannula is constructed of medical grade
polyvinyl chloride.
30. A catheter as defined in claim 27, wherein the distal end of
the balloon is located back from the tip a distance in the range
from about 2 centimeters to about 6 centimeters.
31. A catheter as defined in claim 26, further comprising means
attached to the proximal end of the infusion lumen for introducing
the cardioplegic solution into and through the infusion lumen.
32. A catheter as defined in claim 31, further comprising means
attached to the proximal end of the sensing lumen for sensing the
pressure of the cardioplegic solution at the at least one sensing
lumen orifice.
33. A catheter as defined in claim 31, further comprising means for
stopping the introduction of the cardioplegic solution into the
infusion lumen when the pressure of the cardioplegic solution
exiting the at least one infusion lumen outlet exceeds a
predetermined maximum pressure.
34. A catheter as defined in claim 26, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during the insertion of the cannula into
the coronary sinus and thereby encouraging the sealing engagement
of the balloon with the walls of the coronary sinus.
35. A catheter as defined in claim 34, wherein the balloon taper is
in the range from about 25.degree. to about 35.degree. measured
from the longitudinal axis of the cannula.
36. A catheter as defined in claim 26, wherein the aggregate of
said balloon apertures has a total cross-sectional area in the
range of from about 1.5 to about 5 times the cross-sectional area
of the infusion lumen.
37. A catheter as defined in claim 26, wherein the aggregate of
said balloon apertures has a total cross-sectional area in the
range from about 2 to about 3 times the cross-sectional area of the
infusion lumen.
38. A catheter as defined in claim 26, wherein the balloon, when
filled with cardioplegic solution, has a cross sectional diameter
in the range of from about 1.6 to about 2.0 centimeters.
39. A catheter as defined in claim 26, wherein the balloon when
filled with cardioplegic solution, has a cross-sectional diameter
in the range of from about 1.7 to about 1.8 centimeters.
40. A catheter as defined in claim 26, wherein the dual lumen
cannula is constructed of a material having a softness in the range
from about 75 to about 85 durometer, Shore-A.
41. A catheter as defined in claim 40, wherein the dual lumen
cannula is constructed of medical grade polyvinyl chloride.
42. A catheter as defined in claim 26, wherein the balloon is
constructed of a material having a percent elongation greater than
about 600%.
43. A catheter as defined in claim 42, wherein the balloon is
constructed of polyurethane.
44. A catheter as defined in claim 26, further comprising a
plurality of balloon apertures in the infusion lumen.
45. A catheter as defined in claim 44, wherein the distal end of
the balloon is located back from the tip a distance in the range
from about 2 centimeters to about 6 centimeters.
46. A catheter as defined in claim 45, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during insertion of the cannula into the
coronary sinus and thereby encouraging the sealing engagement of
the balloon with the walls of the coronary sinus, said catheter
further comprising:
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
47. A catheter as defined in claim 44, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during insertion of the cannula into the
coronary sinus and thereby encouraging the sealing engagement of
the balloon with the walls of the coronary sinus, said catheter
further comprising:
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
48. A catheter as defined in claim 26, further comprising a
plurality of infusion lumen outlets in the infusion lumen.
49. A catheter as defined in claim 48, wherein the balloon is
tapered from the distal end to the proximal end of the balloon,
thereby minimizing trauma during insertion of the cannula into the
coronary sinus and thereby encouraging the sealing engagement of
the balloon with the walls of the coronary sinus, said catheter
further comprising:
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula.
50. A catheter as defined in claim 26, wherein the cross-sectional
area of sensing lumen orifice is in the range from about 2 to about
3 times the cross-sectional area of the sensing lumen.
51. A catheter for performing retrograde venous cardioplegia by
delivering a cardioplegic solution into the coronary sinus of the
heart, the catheter comprising:
a flexible, dual lumen cannula of a size capable of insertion into
the coronary sinus of the heart, said cannula having an infusion
lumen and a sensing lumen;
a tip located at the distal end of the cannula such that the distal
ends of the infusion lumen and the sensing lumen are occluded at
the tip, the tip being configured and made of a material such that
trauma to the coronary sinus is minimized during insertion of the
cannula;
a balloon attached about and to the cannula periphery near the
distal end of the cannula, thereby forming a chamber between the
balloon and the cannula, said balloon being tapered from the distal
end to the proximal end of the balloon, thereby minimizing trauma
during the insertion of the cannula into the coronary sinus and
thereby encouraging sealing engagement of the balloon with the
walls of the coronary sinus;
a plurality of balloon apertures in the infusion lumen positioned
such that the infusion lumen is in communication with the chamber
formed by the balloon and the cannula through the balloon
apertures, the aggregate of said balloon apertures having a total
cross-sectional area in the range from about 1.5 to about 5 times
the cross-sectional area of the infusion lumen;
a plurality of infusion lumen outlets in the infusion lumen
positioned between the balloon and the distal end of the cannula
such that, when cardioplegic solution passes through the infusion
lumen, a portion of the cardioplegic solution enters the chamber
through the balloon apertures and a portion of the cardioplegic
solution exits the infusion lumen and the cannula through the
infusion lumen outlets, the aggregate of said infusion lumen
outlets having a total cross-sectional area which is in the range
from about twenty-five to about seventy-five percent cross-section
area of the infusion lumen, thereby creating a pressure within the
infusion lumen which causes the cardioplegic solution to enter the
inner chamber through the balloon apertures in order to fill the
balloon until it is turgid and in sealing engagement with the walls
of the coronary sinus;
at least one sensing lumen orifice in the sensing lumen located at
a point between the balloon and the distal end of the cannula which
is remote from the at least one infusion lumen outlet, said sensing
lumen orifice having a cross-sectional area greater than the
cross-sectional area of the sensing lumen; and
a stylet removably positioned within the flexible cannula, said
stylet having a handle at the proximal end thereof, and a
predetermined curve at the distal end thereof, said stylet being
constructed of a rigid material such that the stylet can be used to
position the flexible cannula in the coronary sinus with minimal
trauma to the heart tissue.
52. A catheter as defined in claim 51, wherein the aggregate of
said balloon apertures has a total cross-sectional area in the
range from about 2 to about 3 times the cross-sectional area of the
infusion lumen.
53. A catheter as defined in claim 51, wherein the balloon, when
filled with cardioplegic solution, has a cross-sectional diameter
in the range of from about 1.6 to about 2.0 centimeters.
54. A catheter as defined in claim 53, wherein the distal end of
the balloon is located back from the tip a distance in the range
from about 2 centimeters to about 6 centimeters.
55. A catheter as defined in claim 54, wherein the balloon is
constructed of a material having a percent elongation greater than
about 600%.
56. A catheter as defined in claim 55, wherein the balloon is
constructed of polyurethane.
57. A catheter as defined in claim 54, wherein the balloon taper is
in the range from about 25.degree. to about 35.degree. measured
from: the longitudinal axis of the cannula.
58. A catheter as defined in claim 54, further comprising means
attached to the proximal end of the infusion lumen for introducing
the cardioplegic solution into and through the infusion lumen.
59. A catheter as defined in claim 58, further comprising means
attached to the proximal end of the sensing lumen for sensing the
pressure of the cardioplegic solution at the sensing lumen
orifice.
60. A catheter as defined in claim 59, further comprising means for
stopping the introduction of the cardioplegic solution into the
infusion lumen when the pressure of the cardioplegic solution
exiting the sensing lumen orifice exceeds a predetermined maximum
pressure.
61. A catheter as defined in claim 54, wherein the tip located at
the distal end of the cannula is constructed of a material having a
softness in the range from about 55 to about 60 durometer,
Shore-A.
62. A catheter as defined in claim 61, wherein the tip located at
the distal end of the cannula is constructed of medical grade
polyvinyl chloride.
63. A catheter as defined in claim 61, wherein the dual lumen
cannula is constructed of a material having a softness in the range
from about 75 to about 85 durometer, Shore-A.
64. A catheter as defined in claim 63, wherein the dual lumen
cannula is constructed of medical grade polyvinyl chloride.
65. A catheter as defined in claim 51, wherein the balloon when
filled with cardioplegic solution, has a cross-sectional diameter
in the range of from about 1.7 to about 1.8 centimeters.
66. A catheter as defined in claim 51, wherein the cross-sectional
area of sensing lumen orifice is in the range from about 2 to about
3 times the cross-sectional area of the sensing lumen.
67. A method for the retrograde administration of a cardioplegic
solution into the coronary sinus of the heart, the method
comprising the steps of:
inserting a catheter through a small incision in the right atrium,
said catheter comprising:
a cannula having an infusion lumen with at least one infusion lumen
outlet near its distal end such that cardioplegic solution can be
introduced into and passed through the cannula and exit the outlet,
said cannula also having a sensing lumen with a sensing lumen
orifice near its distal end having a cross-sectional area greater
than the cross-sectional area of the sensing lumen;
a self-filling balloon secured about the cannula at a point
proximal of the at least one infusion lumen outlet such that as
cardioplegic solution passes through the cannula, a portion of the
cardioplegic solution fills the balloon and a portion exits the
cannula through the outlet; and
a removable curved stylet located within the cannula, said stylet
being constructed of a rigid material;
manipulating the stylet to position the catheter within the
coronary sinus such that the balloon, when filled with cardioplegic
solution, will be in engagement with the walls of the coronary
sinus:
securing the catheter in place in order to minimize longitudinal
movement of the balloon and outlet of cannula within the coronary
sinus;
withdrawing the stylet from within the catheter; and
injecting cardioplegic solution through the cannula at sufficient
pressure such that the balloon fills to sealingly engage the walls
of the coronary sinus, thereby permitting retrograde administration
of the cardioplegic solution.
68. A method for the retrograde administration of cardioplegic
solution as defined in claim 67, further comprising the step of
monitoring the pressure of the cardioplegic solution within the
coronary sinus in order to minimize damage to the coronary sinus by
excessive pressures and flow rates of the cardioplegic
solution.
69. A method for the retrograde administration of a cardioplegic
solution as defined in claim 68, further comprising the step of
terminating the injection of the cardioplegic solution through the
cannula if the fluid pressure within the coronary sinus exceeds a
predetermined maximum pressure.
70. A method for the retrograde administration of cardioplegic
solution as defined in claim 67, further comprising terminating the
injection of the cardioplegic solution through the catheter such
that the self-filling balloon empties to permit normal venous fluid
flow into the right atrium.
71. A method for the retrograde administration of a cardioplegic
solution as defined in claim 70, further comprising the step of
periodically injecting cardioplegic solution through the cannula
and terminating the injection of the cardioplegic solution.
72. A method for the retrograde administration of a cardioplegic
solution as defined in claim 70, wherein after terminating the
injection of the cardioplegic solution, antegrade cardioplegia is
initiated for a period of time.
73. A method for the retrograde administration of a cardioplegic
solution as defined in claim 67, further comprising the step of
maintaining the fluid pressure within the coronary sinus below
about 50 mmHg.
74. A method for the retrograde administration of a cardioplegic
solution as defined in claim 67, wherein the cardioplegic solution
is injected through the cannula at a flow rate in the range from
about 200 ml/min to about 300 ml/min.
75. A catheter for performing retrograde venous cardioplegia by
delivering a cardioplegic solution into the coronary sinus of the
heart, the catheter comprising:
a flexible, dual lumen cannula of a size capable of insertion into
the coronary sinus of the heart, said cannula having an infusion
lumen and a sensing lumen;
a balloon attached to the cannula periphery near the distal end of
the cannula, thereby forming a chamber between the balloon and the
cannula;
at least one balloon aperture in the infusion lumen positioned such
that the infusion lumen is in communication with the chamber formed
by the balloon and the cannula through the at least one balloon
aperture, the aggregate of said balloon apertures having a total
cross-sectional area which is greater than the cross-sectional area
of the infusion lumen;
at least one infusion lumen outlet in the infusion lumen positioned
between the proximal end of the balloon and the distal end of the
cannula such that, when cardioplegic solution passes through the
infusion lumen, the size and configuration of the at least one
infusion outlets creates a pressure within the infusion lumen which
cause the cardioplegic solution enters the chamber through the at
least one balloon aperture in a order to fill the balloon until it
is turgid and in sealing engagement with the walls of the coronary
sinus; and
at least one sensing lumen orifice in the sensing lumen located at
a point proximal of the distal end of the cannula which is remote
from the at least one infusion lumen outlet, the aggregate of said
sensing lumen orifices having a cross-sectional area greater than
the cross-sectional area of the sensing lumen.
76. A method for the retrograde administration of a cardioplegic
solution into the coronary sinus of the heart, the method
comprising the steps of:
(a) inserting a catheter through a small incision in the right
atrium, said catheter comprising:
a cannula having an infusion lumen with at least one infusion lumen
outlet near its distal end such that cardioplegic solution can be
introduced into and passed through the cannula and exit the outlet,
said cannula also having a sensing lumen with at least one sensing
lumen orifice near its distal end, the aggregate of said sensing
lumen orifices having a total cross-sectional area greater than the
cross-sectional areas of the sensing lumen;
a self-filling balloon secured about the cannula at a point
proximal of the at least one infusion lumen outlet such that as
cardioplegic solution passes through the cannula, a portion of the
cardioplegic solution fills the balloon and a portion exits the
cannula through the outlet; and
a removable curved stylet located within the cannula;
(b) manipulating the stylet to position the catheter within the
coronary sinus such that the balloon, when filled with cardioplegic
solution, will be in engagement with the walls of the coronary
sinus;
(c) securing the catheter in place in order to minimize
longitudinal movement of the balloon and outlet of cannula within
the coronary sinus;
(d) withdrawing the stylet from within the catheter; and
(e) injecting cardioplegic solution through the cannula at
sufficient pressure such that the balloon fills to sealingly engage
the walls of the coronary sinus, thereby permitting retrograde
administration of the cardioplegic solution.
77. A catheter for performing retrograde venous cardioplegia by
delivering a cardioplegic solution into the coronary sinus of the
heart, the catheter comprising:
a flexible, cannula of a size capable of insertion into the
coronary sinus of the heart, said cannula having an infusion lumen
and a sensing lumen;
a balloon attached to the cannula periphery near the distal end of
the cannula, thereby forming a chamber between the balloon and the
cannula;
at least one balloon aperture in the infusion lumen positioned such
that the infusion lumen is in communication with the chamber formed
by the balloon and the cannula through the at least one balloon
aperture;
at least one infusion lumen outlet in the infusion lumen positioned
between the proximal end of the balloon and the distal end of the
cannula such that, when cardioplegic solution passes through the
infusion lumen, the size and configuration of the at least one
infusion outlets creates a pressure within the infusion lumen which
causes the cardioplegic solution enters the chamber through the at
least one balloon aperture in a order to fill the balloon until it
is turgid and in sealing engagement with the walls of the coronary
sinus;
at least one sensing lumen orifice in the sensing lumen located at
a point proximal of the distal end of the distal end of the cannula
which is remote from the at least one infusion lumen outlet, the
aggregate of said sensing lumen orifices having a cross-sectional
area greater than the cross-sectional area of the sensing lumen;
and
a stylet removably positioned within the flexible cannula, said
stylet having a handle at the proximal end thereof and a
predetermined curve at the distal end thereof, said stylet handle
having a finger loop extending from the distal end of the stylet
handle and a thumb rest located at the proximal end of the stylet
handle.
78. A catheter for performing retrograde venous cardioplegia as
defined in claim 77, wherein the stylet handle is configured such
that placement of a surgeon's index finger against the finger loop,
the ring finger against the stylet handle, and the thumb against
the thumb rest enables the catheter to be quickly inserted with the
coronary sinus with a slight twist of the surgeon's wrist.
79. A catheter for performing retrograde venous cardioplegia as
defined in claim 77, wherein the stylet handle is configured such
that placement of a surgeon's index finger against the finger loop,
the ring finger against the stylet handle, and the thumb against
the thumb rest enables the catheter to be quickly inserted with the
coronary sinus with a slight twist of the surgeon's wrist.
Description
BACKGROUND
1. The Field of the Invention
The present invention is directed to retrograde cardioplegia
catheters and the methods of their use and manufacture. More
particularly, the catheters of the present invention are designed
for rapid and accurate insertion into the coronary sinus and for
retrograde administration of cardioplegia with maximum
effectiveness and minimum tissue damage.
2. The Prior Art
Since the early days of cardiac surgery, it has been recognized
that in order to provide the optimum surgical conditions when
operating on the heart, it is necessary to interrupt the normal
operation of the heart. For obvious reasons, an arrested, flaccid
heart is preferred during a cardiac surgical procedure over a
beating heart with blood s flowing through it. Thus, in order to be
able to efficiently perform cardiac surgery, it is often necessary
to use cardiopulmonary-bypass techniques and to isolate the heart
from its life-giving blood supply.
It has been found that many deaths occurring after cardiac surgery
are due to acute cardiac failure. At first, it was believed that
the heart was simply beyond repair and that the operation had
failed to correct the problem. Later, it was discovered that many
of these postoperative deaths were due to new, and often extensive,
perioperative (during or within 24 hours after the surgical
procedure) myocardial necrosis (death of the heart tissue).
Furthermore, many patients who survived were found to have suffered
myocardial necrosis to a significant degree, thereby resulting in
low cardiac blood output.
It is now known that myocardial necrosis occurs because the energy
supply or reserve of the cardiac muscle cells is inadequate to
supply the needs of the heart. The availability of oxygen
dramatically affects the cell s ability to satisfy these energy
requirements. For example, anaerobic metabolism of glucose produces
two (2) moles of adenosine triphosphate ("ATP") per mole of glucose
(as well as harmful acid metabolites), whereas aerobic metabolism
of glucose produces thirty-six (36) moles of ATP per mole of
glucose. Therefore, one of the primary goals of myocardial s
preservation techniques during surgery is to reduce myocardial
oxygen consumption.
Myocardial oxygen consumption is significantly reduced by stopping
the electromechanical work of the heart. The oxygen demands of the
beating empty heart at 37.degree. C. are four to five times those
of the arrested heart (i.e., 4-5 ml/100-gm/min compared with 1
ml/100-gm/min). Buckberg, G. D., "Strategies and Logic of
Cardioplegic Delivery to Prevent, Avoid, and Reverse Ischemic and
Reperfusion Damage," 93 The Journal of Thoracic and Cardiovascular
Surgery, 127, 136 (Jan. 1987) (hereinafter referred to as:
Buckberg, "Strategies and Logic of Cardioplegic Delivery").
Oxygen consumption can be reduced further by cooling the heart. For
example, the oxygen requirements of the arrested heart at
20.degree. C. are 0.3 ml/100-gm/min and are reduced to only 0.15
ml/100-gm/min at 10.degree. C. On the other hand, the oxygen
requirements of the beating or fibrillating heart at comparable
temperatures, are 2-3 ml/100-gm/min. Buckberg, "Strategies and
Logic of Cardioplegic Delivery" at 129.
The normal heart receives its blood supply through the left and
right coronary arteries which branch directly from the aorta.
Generally, the veins draining the heart flow into the coronary
sinus which empties directly into the right atrium. A few veins,
known as thebesian veins, open directly into the atria or
ventricles of the heart.
One of the early methods utilized to protect the myocardium during
surgery was normothermic perfusion of the empty beating heart. This
method was utilized in an effort to maintain the heart, as near as
possible, in normal conditions during surgery. Although the
procedure eliminated the problem of blood flow, dissection and
suturing were still difficult to perform because of the firmness of
the myocardium and the beating of the heart. Additionally, it was
found that a significant amount of damage still occurred to the
myocardium when this procedure was utilized.
A second method which was developed to protect the myocardium was
intermittent cardiac ischemia with moderate cardiac hypothermia.
This method requires that the entire body be perfused at a
temperature of from 28.degree. C. to 32.degree. C., thus slowing
all bodily functions, including those of the heart. The heart is
fibrillated before aortic crossclamping to stop the beating. The
surgeon can then operate for approximately fifteen to twenty-five
(15-25) minutes, after which time the heart beat is necessarily
resumed for three to five (3-5) minutes. This procedure proved to
be an inefficient method for performing operations and had many
attendant dangers, including the fibrillation of the heart.
A third method which has been utilized is profound hypothermic
cardiac ischemia. This method requires that the temperature of the
heart be lowered to about 22.degree. C. by the infusion of a cooled
perfusate and/or by filling the pericardium with cold saline
solution. One of the major disadvantages of this technique is that
the heart continues to fibrillate, exhausting the heart's stored
energy. As a result, the heart becomes acidotic, which over time
causes irreversible muscle damage.
A fourth method which has been developed to preserve the myocardium
during surgery is the infusion of a cold cardioplegic fluid to cool
and stop the beating of the heart After the initial infusion, the
heart is reperfused approximately every thirty (30) minutes to
maintain the cool, dormant state of the heart.
The use of cardioplegia to protect the myocardium has proven the
most advantageous method of those used to date. Cardioplegia, which
literally means "heart stop," may be administered in an antegrade
manner (through arteries in the normal direction of blood flow), in
a retrograde manner (through veins opposite the normal blood flow
direction), or in a combination of retrograde and antegrade
administration. Cardioplegic solutions, typically containing
potassium, magnesium procaine, or a hypocalcemic solution, stop the
heart by depolarizing cell membranes.
Cardioplegia may be induced immediately after extracorporeal
circulation has begun, provided that the pulmonary artery is
collapsed to attest to the adequacy of venous return. In normal
antegrade cardioplegia, a single venous return catheter is inserted
in the right atrium to transfer the blood from the body to the
heart-lung machine which a single needle is inserted into the aorta
beneath the clamp through which the cardioplegic solution is
administered. The cardioplegic solution flows through the coronary
arteries in the normal blood flow direction.
If aortic insufficiency exists (imperfect closure of the aortic
valve) or the patient is undergoing aortic valve replacement, then
direct cannulation of the coronary arteries is necessary to perform
antegrade cardioplegia. In this technique the aortic root is opened
(using the procedure called "aortotomy") and perfusion catheters
are inserted into both the left and right coronary ostia.
Care must be taken to avoid mechanical injury to the coronary ostia
which could produce the serious complications of coronary ostial
stenosis (i.e. constricting of the coronary ostia). Ostial stenosis
requires reparative surgery and can be quite hazardous due to
obstruction of the coronary arteries. Moreover, it is a nuisance to
have perfusion catheters present within the limited operative field
during aortic valve replacement. The inconvenience and time
consumed by positioning perfusion catheters have led to
dissatisfaction with direct coronary perfusion.
The foregoing risks and inconvenience of direct coronary
cannulation may be avoided by using the retrograde cardioplegia
technique. For this reason, some surgeons select retrograde
cardioplegia as the preferred method of myocardial protection
during aortic valve replacement.
Retrograde cardioplegia is conventionally administered by inserting
a balloon catheter within the coronary sinus, inflating the balloon
to stop the normal fluid flow into the right atrium, and perfusing
the cardioplegic solution backwards through the coronary veins. In
order to insert the catheter into the coronary sinus, the right
heart must be isolated. To isolate the right heart, both the
superior and inferior venae cavae must be tied and each must be
cannulated. Once the right heart is isolated, the right atrium may
be opened without allowing air to enter the circulatory system,
thereby reducing the risk of systemic air embolization.
With the right atrium open, the catheter is visually inserted into
the coronary sinus and hand-held while the cardioplegic solution is
administered. The right atrium is then closed. This process must be
repeated each time cardioplegic solution is administered during the
operation. See Buckberg, "Strategies and Logic of Cardioplegic
Delivery" at 132-33.
Retrograde cardioplegia is more complicated than antegrade
cardioplegia because it requires right heart isolation, right
atriotomy (i.e. opening the right atrium), and hand-holding the
catheter during perfusion. Furthermore, retrograde cardioplegia may
result in undesirable consequences.
For example, the atriotomy may lead to heart arrhythmia, and
repeated cannulation may substantially injure the coronary sinus.
In addition, high perfusion pressure or the failure to periodically
allow normal venous drainage may damage the coronary veins and
microcirculatory system causing edema. For these reasons, some
surgeons completely avoid retrograde cardioplegia.
Nevertheless, there are some situations where retrograde
cardioplegia is advisable over antegrade. For example, antegrade
cardioplegia produces nonhomogeneous cooling and cardioplegic
maldistribution in cases of myocardial ischemia and diffuse
coronary disease. Antegrade cardioplegia does not adequately
protect those areas of the heart downstream from coronary artery
obstructions.
Several surgical graft techniques have been developed to circumvent
coronary artery obstructions. In almost all of these techniques,
cardioplegic solution is delivered down the grafts after they are
completed. The graft is first attached to the coronary artery below
the blockage, thereby leaving the other end of the graft open
through which the cardioplegic solution can be administered. The
open end of the graft is then attached to the aorta. Unfortunately,
the area of the heart downstream of the obstruction does not
receive any cardioplegic protection until after the graft is
attached.
In the case of diffuse coronary artery disease, not all of the
coronary blockages receive grafts. Therefore, the areas that are
not grafted receive very minimal protection. In these situations,
only retrograde cardioplegia can adequately protect those areas of
the heart downstream from the coronary blockages.
Recently, some surgeons have begun using the internal mammary
artery as the preferred graft for use on patients with coronary
artery disease. It has been found that the internal mammary artery
provides a superior long-term graft over the customary vein grafts
(e.g., saphenous vein grafts). However, because the internal
mammary artery remains proximally intact and insertion of a needle
into the mammary artery would severely damage the artery, antegrade
cardioplegia cannot be delivered through the internal mammary
artery.
Many surgeons choose not to use internal mammary grafts in patients
who have more severe forms of heart disease because antegrade
cardioplegia is not available to protect the heart, notwithstanding
the graft's superiority. Because antegrade cardioplegia does not
adequately protect the heart downstream of the graft, that part of
the heart muscle may be permanently damaged, resulting in a
mortality or a very complicated, prolonged convalescence.
Although retrograde cardioplegia would provide adequate protection
for those patients undergoing an internal mammary graft, surgeons
often opt to use antegrade cardioplegia in combination with the
inferior saphenous vein graft in order to avoid the cumbersome
retrograde cardioplegia technique. The net result is that the sick
patient receives a good short-term benefit by surviving the
operation. But many years later, the patient has an inferior graft
which may require additional surgery.
Furthermore, it has been found that by combining retrograde and
antegrade cardioplegia many of the limitations inherent in the two
protection strategies may be overcome so that a more uniform degree
of myocardial hypothermia and complete regional and global left and
right ventricular functional recovery is possible. Nevertheless,
clinical adoption of retrograde cardioplegic techniques, alone or
in combination with antegrade techniques, has been slow despite
evidence of its usefulness. The principle reason for this delay in
clinical acceptance seems to stem from the more cumbersome
operative technique that is required to employ retrograde
cardioplegia.
Most cardiac operations in adult patients are performed with single
venous cannulation. Thus, the need for double cannulation of the
venae cavae and isolation of these vessels, right atriotomy, and
hand-holding of the catheter in the coronary sinus are all
additional surgical procedures required in order to perform
retrograde cardioplegia. These additional procedures, combined with
possible isolation of the pulmonary artery, slower time to arrest,
and possible large volumes of the cardioplegic solution needed to
fill the right heart have limited the acceptance of current
retrograde techniques.
In summary, retrograde cardioplegia often can provide superior
myocardial protection over antegrade cardioplegia alone and the
combination of retrograde cardioplegia and antegrade cardioplegia
can provide superior myocardial protection than either technique
alone. Yet there is substantial resistance by many surgeons to take
advantage of the benefits of retrograde cardioplegia because it
complicates an already complex surgical procedure.
From the foregoing, it will be appreciated that what is needed in
the art are apparatus and methods for performing retrograde
cardioplegia which are simple and effective so that the advantages
of retrograde cardioplegia can be readily utilized by surgeons.
Additionally, it would be a significant advantage over the art to
provide apparatus and methods for performing retrograde
cardioplegia which do not require right atrial isolation, right
atriotomy, and repeated cannulation of the catheter.
It would be another advancement in the art to provide a retrograde
cardioplegia catheter which can be quickly and accurately inserted
within the coronary sinus with relatively little trauma to the
patient.
It would be yet another advancement in the art to provide apparatus
and methods for performing retrograde cardioplegia which allow
surgeons to safely use the internal mammary graft without making
the surgical procedure cumbersome.
The foregoing, and other features and objects of the present
invention, are realized in the retrograde cardioplegia catheter
apparatus and method which are disclosed and claimed herein.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION
The present invention is directed to retrograde cardioplegia
catheters and their methods of use and manufacture. The catheters
of the present invention include two lumens--a large lumen through
which the cardioplegic solution flows and a smaller lumen which may
be connected to a pressure sensing device for monitoring the fluid
pressure at the point where the cardioplegic solution exits the
catheter into the coronary sinus.
A self-filling balloon is secured near the distal end of the
catheter. In the preferred embodiment of the present invention, the
self-filling balloon is slightly tapered. A plurality of apertures
in the larger lumen open into the self-filling balloon. These
apertures allow the cardioplegic solution to fill the balloon while
the fluid is flowing, but when the fluid stops, the balloon
empties.
A low-trauma tip occludes the distal end of the catheter The tip is
rounded and soft to prevent damage to the sensitive intimal tissues
of the coronary sinus. The larger lumen includes plurality of small
openings located between the low-trauma tip and the self-filling
balloon which allow the cardioplegic solution to exit the
catheter.
A removable stylet, or "introducer," is located within the large
lumen. The stylet has a predetermined curve at the distal end
thereof and a handle at the proximal end which permit rapid and
accurate positioning of the catheter within the coronary sinus. The
stylet enables the catheter to be inserted within the coronary
sinus through a very small incision made in the right atrium, as
opposed to a relatively large incision (about three (3) centimeters
long) necessary when the current retrograde cardioplegic technique
is used.
The predetermined curve at the proximal end of the stylet permits
rapid and accurate positioning of the catheter within the coronary
sinus. The catheter is then simply secured in place with a purse
string suture, and the stylet is withdrawn from the catheter. Once
securely positioned, the catheter remains in place for the duration
of the operation. It will be appreciated, that the method of using
the present invention avoids right atrial isolation, right
atriotomy, repeated cannulation of the catheter, and hand-holding
of the catheter during retrograde perfusion of the cardioplegic
solution.
As the cardioplegic solution flows through the large lumen of the
catheter of the present invention, the self-filling balloon fills
to seal the coronary sinus and to prevent the solution from flowing
into the right atrium. The small lumen is operatively connected to
a pressure sensing device which monitors the pressure within the
coronary sinus. If the pressure becomes too great, the flow of
cardioplegic solution is automatically stopped, allowing the
balloon to empty and the solution to drain into the right
atrium.
It is, therefore, an object of the present invention to provide
apparatus and methods for performing retrograde cardioplegia which
are simple and effective so that the advantages of retrograde
cardioplegia can be readily utilized by surgeons.
Another important object of the present invention is to provide
apparatus and methods for performing retrograde cardioplegia which
do not require right atrial isolation, right atriotomy, and
repeated cannulation of the apparatus.
An additional object of the present invention is to provide a
retrograde cardioplegia catheter which may be quickly and
accurately positioned within the coronary sinus.
Still another object of the present invention is to provide
apparatus and methods for performing retrograde cardioplegia which
allow surgeons to safely use the lifesaving internal mammary graft
without making the surgical procedure cumbersome.
These and other objects and features of the present invention will
become more fully apparent from the following description and
appended claims taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of one presently preferred embodiment
within the scope of the present invention.
FIG. 2 is a cross-sectional view of the distal end of the
embodiment illustrated in FIG. 1 taken along line 2--2 of FIG.
1.
FIG. 3 is a perspective view illustrating a preferred embodiment of
the retrograde cardioplegic catheter of the present invention, when
inserted within the coronary sinus of the heart.
FIG. 4 is a partial cross-sectional perspective view of the
retrograde cardioplegic catheter within the coronary sinus taken
along line 4--4 of FIG. 3.
FIG. 5 is a perspective view illustrating a preferred embodiment of
the present invention when used in combination with antegrade
cardioplegia.
FIG. 6 is a cross-sectional view of a mandrel used in manufacturing
a self-filling balloon within the scope of the present
invention.
FIG. 7 is a cross-sectional view of the mandrel shown in FIG. 6 in
which the balloon is beginning to separate from the mandrel due to
the injection of a releasing fluid.
FIG. 8 is a plan view of a balloon removed from the mandrel and
prepared for attachment to the flexible cannula.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A. The Retrograde Cardioplegia Catheters
Reference is now made to the drawings wherein like parts are
designated with like numerals throughout. Referring first to FIGS.
1 and 2, one presently preferred embodiment of an apparatus within
the scope of the present invention is illustrated and generally
designated 10.
Catheter 10 is particularly designed for the retrograde venous
administration of cardioplegic solutions. The apparatus includes a
flexible cannula 12 having a soft, rounded tip 14 at the distal end
and a coupling device 16 at the proximal end for attaching the
catheter to a cardioplegic solution source. The cardioplegic
solution would typically be provided through either a volumetric
pump or a bag of solution within a pressure cuff.
Flexible cannula 12 contains two lumens: an infusion lumen 18 for
introducing the cardioplegic solution into the coronary sinus and a
pressure-sensing lumen 20 for monitoring the fluid pressure within
the coronary sinus.
The flexible cannula is preferably constructed of a material which
retains its flexibility after prolonged exposure to temperatures of
at least about 0.degree. C. In one current preferred embodiment,
flexible cannula 12 is constructed of medical-grade polyvinyl
chloride, having a softness of about 75 to 85 durometer, Shore-A.
Other suitable materials, may also be used to construct flexible
cannula 12, such as medical-grade silicone and polyurethane.
It is important that the flexible cannula be flexible enough to
manipulate and position within the coronary sinus, but also have
sufficient rigidity and structural integrity to not collapse or
bend to cut off flow of the cardioplegic solution during use. In
addition, the flexible cannula should be soft enough to compress or
deflect when pressed against the coronary sinus, thereby protecting
the coronary should not be so soft that a tie holding it in place
occludes the cannula.
As best illustrated in FIG. 2, soft, rounded tip 14 occludes the
end of both infusion lumen 18 and pressure-sensing lumen 20. The
soft rounded tip is preferably constructed of a material which will
minimize the trauma and the risk of intimal damage to the coronary
sinus and other heart tissues during insertion and use.
In one presently preferred embodiment of the present invention, the
rounded tip is constructed of medical-grade polyvinyl chloride,
having a softness of about 55 to 60 durometer, Shore A. Other
suitable materials may be used to construct the rounded tip such as
silicone and polyurethane.
In one presently preferred embodiment, the rounded tip is
constructed with two small appendages formed to fit within the
infusion and pressure-sensing lumens. The fit between the rounded
tip and the outer wall of flexible cannula 12 should be smooth to
reduce the possibility of an exposed uneven edge injuring sensitive
heart tissues.
The rounded tip is preferably solvent bonded to the distal end of
the flexible cannula. It is important that the solvent maintains a
seal or bond between the rounded tip and the end of the lumens
during use. Additionally, the solvent should not create a hard
surface which could cause trauma during insertion, use, or removal.
Cyclohexanone is the presently preferred solvent, but other
solvents such as butanone (methyl ethyl keton), tetrahydrofuran
("THF"), and methylene chloride are possible suitable
substitutes.
A self-filling balloon 22 is located near the distal end of
flexible cannula 12, slightly proximal from rounded tip 14.
Self-filling balloon 22 forms an inner chamber 24 inside the
balloon and outside cannula. In one embodiment of the present
invention, the distal end of the self-filling balloon is located
approximately 2.0 cm to approximately 6.0 cm back from the rounded
tip. Such an embodiment permits rounded tip 14 to be inserted far
into the coronary sinus, yet still permit the self-filling balloon
to seal the coronary sinus. For most purposes, the distal end of
the self-filling balloon is preferably located about 2.0 cm to a
bout 3.5 cm back from the rounded tip.
One preferred method of attaching the self-filling balloon to the
flexible cannula is solvent bonding with tetrahydrofuran, though
other solvents such as dimethylformamide ("DMF"), acetone, and
cyclohexanone, for example, could be substituted. The balloon is
attached to the flexible cannula according to techniques well-known
in the art.
In the preferred embodiment of the present invention, the balloon
is slightly tapered, increasing in diameter from the distal end to
the proximal end of the balloon. The taper allows cardioplegic
solution to be infused into the more distal branches of the
coronary sinus, thereby providing thorough cardioplegic protection.
A cylindrically shaped balloon might readily occlude the ostia of
the more distal branches of the coronary sinus which may be as
close as 0.5 cm from the entry of the sinus into the right atrium.
If the ostia are occluded, then portions of the heart upstream from
the ostia would not receive cardioplegic protection.
A taper in the range of from about 25.degree. to about 35.degree.,
measured from the longitudinal axis of the flexible cannula has
been found to be suitable. Other larger or smaller tapers may be
used. However, if the taper is too great, then the balloon is
difficult to properly insert and position within the coronary
sinus, and there is more likelihood of trauma to the tissues as the
cannula is inserted and positioned. If the taper is too small, then
the balloon becomes too long to fit within the coronary sinus and
still engage the walls.
In addition, it has been found that a balloon taper within the
range of the present invention performs a unique self-centering
function which facilitates quick and accurate placement of the
catheter within the coronary sinus.
A plurality of balloon apertures 26 in infusion lumen 18 allow the
flowing cardioplegic solution to inflate the balloon. The balloons
of most balloon catheters known in the art expand and collapse
depending upon the fluid pressure within the balloon compared with
the fluid pressure outside the balloon. It has been found that the
pressure required to inflate conventional balloon catheters to seal
the coronary sinus often results in an excessive infusion pressure.
In addition, the low operating fluid pressures used in connection
with the present invention could not adequately inflate
conventional balloon catheters.
In response to this problem, the self-filling balloon of the
present invention is constructed so that it is not necessary for
the balloon to expand significantly from its unfilled state in
order to seal the coronary sinus. Thus, upon filling, the balloon
becomes turgid but not significantly distended beyond the balloon's
original shape.
The self-filling balloon preferably has a cross-sectional diameter
which is slightly larger than the cross-sectional diameter of the
coronary sinus. A typical adult coronary sinus has a diameter in
the range of from about 1.4 cm to about 1.6 cm. Hence, in most
individuals, a balloon having a cross-sectional diameter in the
range of from about 1.6 cm to 2.0 cm will work.
In one current preferred embodiment of the present invention, the
balloon has a cross-sectional diameter from about 1.7 cm to about
1.8 cm. Upon insertion within the coronary sinus, when the balloon
has not been filled with cardioplegic solution the balloon becomes
slightly wrinkled about its outer periphery due to the smaller
diameter of the cardioplegic solution the balloon is filled and
becomes turgid in order to sealingly engage the walls of the
coronary sinus.
It will be appreciated that the coronary sinus of pediatric
patients will be somewhat smaller than that of an adult patient. As
a result, a retrograde cardioplegia catheter designed for pediatric
use is necessarily designed so that the a self-filling balloon has
a diameter to fit within the coronary sinus of the patient.
The total cross-sectional area of balloon apertures 26 is
preferably between approximately 1.5 to approximately 5 times the
cross-sectional area of infusion lumen 18 to facilitate rapid
filling and emptying of the balloon. In the presently preferred
embodiment within the scope of the present invention, the total
cross-sectional area of apertures 26 is about 2 to 3 times the
cross-sectional area of the infusion lumen.
The embodiment illustrated FIGS. 1 and 2 shows two balloon
apertures 26. The number of openings is dependent on various
factors. On the one hand, the total cross-sectional area of the
apertures must be large (relative to the cross-sectional area of
the infusion lumen) in order for the balloon to be self-filling. On
the other hand, too many apertures or too large or improperly
configured apertures can compromise the structural integrity of the
catheter, thereby causing the tube to bend and/or collapse during
use and inhibit flow of cardioplegic solution through the
catheter.
Thus, there is a balance between having enough properly shaped and
sized openings to create a large total cross-sectional area and
having too many openings which weaken the catheter. In addition,
the difficulty of cutting holes in the infusion lumen without
damaging the pressure-sensing lumen must be considered in
determining the number of balloon openings 26. Hence, while more or
fewer apertures can be readily made to work, two have been found to
be satisfactory for most situations.
A plurality of small infusion lumen outlets 28 located between the
balloon and the rounded tip allow the cardioplegic solution to exit
the catheter. It has been found that the total cross-sectional area
of infusion lumen outlets 28 should be less than the
cross-sectional diameter of the balloon openings 26. In the
presently preferred embodiment, the total cross-sectional area of
infusion lumen outlets 28 is in the range from about twenty-five
percent (25%) to about seventy-five percent (75%) the
cross-sectional area of infusion lumen 18. In the presently
preferred embodiment, the total cross-sectional area of infusion
lumen outlets 28 is approximately fifty percent (50%) the
cross-sectional area of infusion lumen 18.
In one preferred embodiment of the present invention there are six
infusion lumen outlets, three on each side of infusion lumen 18
spaced about 0.2 inches apart and starting about 0.5 cm back from
the rounded tip, each outlet having a diameter of about 0.03 inches
which provides for a total cross-sectional area of the infusion
lumen outlets of about fifty percent (50%) the total
cross-sectional area of the infusion lumen. The cross-sectional
area of the infusion lumen is in the range of from about 0.007
square inches to 0.009 square inches, and preferably about 0.008
square inches.
The primary factor to consider in determining the number and size
of the infusion lumen outlet is the resulting total cross-sectional
area percentage compared to the cross-sectional area of the balloon
aperture and/or the infusion lumen. However, care should be taken
so that the infusion lumen outlets are not so small that the
cardioplegic solution exits the catheter in a jet-like flow which
could harm the coronary sinus. To further reduce any potential
trauma to the coronary sinus from the exiting cardioplegic
solution, the infusion lumen outlets are preferably bored in the
infusion lumen at an angle so that the cardioplegic solution exits
the catheter in a forward direction.
Because the total cross-sectional area of balloon aperture 26 is
preferably substantially greater than the total cross-sectional
area of infusion lumen outlets 28, the fluid pressure of flowing
cardioplegic solution within the balloon inner chamber is greater
than the fluid pressure at the point the solution exits the
catheter. In this way, the self-filling balloon automatically fills
as cardioplegic solution flows through the infusion lumen. When
cardioplegic solution flow stops, the balloon empties as the
solution drains into the coronary sinus.
A sensing lumen orifice 30 near the distal end of pressure-sensing
lumen 20 permits sensing of the fluid pressure at the point where
the cardioplegic solution exits the catheter within the coronary
sinus. It is important to closely monitor the pressure within the
coronary sinus, because if the fluid pressure exceeds a
predetermined maximum pressure (as discussed in greater detail
hereinafter), tissue damage and edema to the coronary sinus and
other heart tissues will likely result. The cross-sectional area of
sensing lumen orifice 30 is preferably greater than the
cross-sectional area of pressure-sensing lumen 20. In the presently
preferred embodiment, the cross-sectional area of sensing lumen
orifice 30 is in the range from about 2 to about 3 times the
cross-sectional area of pressure-sensing lumen 20.
A pressure-sensing feed line 32, which is an extension of
pressure-sensing lumen 20, branches from flexible cannula 12 near
the proximal end of the catheter. A three-way stopcock 34 is
located at the proximal end of pressure-sensing feed line 32. The
three-way stopcock permits coupling to a pressure-sensing device at
one setting, removing air from the pressure-sensing lumen at a
second setting, and sealing the feed line at the third setting. The
pressure-sensing lumen is occluded at a point proximal to the point
feed line 32 branches from the flexible cannula to prevent
introduction of cardioplegic solution into the pressure-sensing
lumen.
A removable stylet 36 is located within flexible cannula 12, the
stylet has at the distal end a predetermined curve and at the
proximal end a stylet handle 38. The stylet handle contains a thumb
rest 40 located at the proximal end thereof. A loop 42 extends
outward from the stylet handle in the same general direction as the
predetermined curve. The stylet is preferably constructed out of a
rigid material, such as a metal rod.
A pair of rings 44 are located just distal of the point where
pressure-sensing feed line 32 branches from flexible cannula 12.
Rings 44 define a suture groove 46 therebetween. The suture groove
enables the catheter to be tied in place after insertion within the
coronary sinus. It is important to tie the catheter in position to
minimize longitudinal movement of the catheter in the coronary
sinus.
A clamp 48 is located on flexible cannula 12 between rings 44 and
the point were the pressure sensing feed line branches from the
flexible cannula. This clamp seals the infusion lumen and inhibits
relative movement of the stylet vis-a-vis the catheter while the
catheter is being inserted with the coronary sinus.
B. Methods of Using the Retrograde Cardioplegia Catheter
Referring now to FIG. 3, catheter 10 is inserted into a small
incision which has been made in the right atrium. The incision is
preferably less than one centimeter long and is about 1 inch to
about 2 inches from the entrance of the coronary sinus 50. A
pulse-string suture is placed to seal the right atrium incision
around the catheter.
Because the right atrium is not completely opened by the methods of
the present invention, it is not necessary to isolate the right
heart by tying and cannulating both venae cavae. This not only
simplifies the surgical procedure, but also reduces the trauma
experienced by the patient. In addition, because the incision in
the right atrium is very small, there is little risk that the
patient will develop a heart arrhythmia which often occurs when the
right atrium is opened.
The curved stylet enables the catheter to be accurately positioned
within the coronary sinus through such a small incision in the
right atrium without visually seeing the coronary sinus. The unique
stylet handle configuration gives the surgeon many options for
holding the stylet and inserting the catheter within the coronary
sinus. These options vary depending on the operating room
condition, the position of the patient's heart, and the surgeon's
own preference.
In one use of the present invention, the surgeon, standing on the
patient's right side, presses the right index finger against loop
42, the right ring finger against stylet handle 38, and the thumb
against thumb rest 40. In this position, the catheter is quickly
inserted within the coronary sinus with a slight twist of the wrist
by moving the index finger towards oneself and the thumb away from
oneself while keeping the ring finger relatively stationary.
If the surgeon is standing on the patient's left side, it may be
preferable to place the ring finger against the loop and the index
finger against the stylet handle. The catheter can be quickly
inserted by moving the ring finger towards oneself and the thumb
away from oneself while keeping the index finger relatively
stationary. The above grips may be reversed and modified if the
surgeon prefers using the left hand.
Once in position, the catheter is secured with a purse-string
suture around the incision in the right atrium. The stylet is then
withdrawn, and suture groove 46 is tied to the tourniquet tube of
the purse-string suture as shown in FIG. 3 to prevent longitudinal
movement of the catheter in the coronary sinus. The catheter
remains in its proper position through the duration of the surgical
procedure. Thus, there is no need to either repeatedly insert the
catheter within the coronary sinus or hand-hold the catheter during
the procedure. In this way, trauma to the coronary sinus is reduced
and simplification of the procedure are achieved.
When the catheter is inserted within the coronary sinus, stylet 36
seals the infusion lumen and three-way stopcock 34 seals the
pressure-sensing lumen. After insertion, the air within both the
infusion and pressure sensing lumens is vented.
To accomplish this, a syringe is attached to coupling device 16 in
order to remove any air from the infusion lumen. Clamp 48 is then
closed until the coupling device is attached to a cardioplegic
solution source. Similarly, the three-way stopcock is adjusted to
permit removal of air from the pressure-sensing lumen. The
three-way stopcock is then attached to a pressure-sensing
device.
Conventional cardioplegic solutions known in the art may be used in
performing retrograde cardioplegia within the scope of the present
invention. The same cardioplegic solution source used for
performing retrograde cardioplegia may be used for performing
retrograde and antegrade cardioplegia in combination.
Generally, regardless of the type of surgical procedure involved, a
venous return catheter 52 shown in FIG. 3 would be required to
enable extracorporeal circulation. Therefore, the method for
retrograde administration of cardioplegic solutions disclosed
herein does not significantly complicate the surgical procedure
compared to present retrograde cardioplegia methods.
FIG. 4 illustrates the proper placement of the catheter within
coronary sinus 50. Self-filling balloon 22 is positioned just
within coronary sinus orifice 54 of right atrial wall 56. As the
cardioplegic solution flows through infusion lumen 18, the fluid
flows through openings 26 to fill the self-filling balloon. Upon
filling, the self-filling balloon is turgid but not significantly
distended beyond its original shape.
During infusion of the cardioplegic solution, the fluid pressure
within the coronary sinus is monitored. If the pressure rises above
a predetermined maximum pressure, then infusion of the cardioplegic
solution is stopped. Once infusion of the cardioplegic solution
stops, the balloon empties to allow normal antegrade flow into the
right atrium. The catheter does not need to be removed to allow for
normal antegrade flow.
It has been found that if the pressure within the coronary sinus
exceeds about 60 mm Hg, venular damage and hemorrhage may result.
It will be appreciated that this maximum pressure may vary from
patient to patient, but this pressure is a conservative maximum
pressure. Therefore, the pressure within the coronary sinus is
preferably maintained below approximately 50 mm Hg in order to
provide a margin of error.
The pressure within the inner chamber of the self-filling balloon
will be somewhat greater than the pressure within the coronary
sinus due to the pressure drop associated with the infusion lumen
outlets. Since excessive pressure within the balloon may cause the
balloon to expand and injure the coronary sinus, the pressure
within the balloon is preferably maintained below about 150 mm
Hg.
Because of the pressure drop through the infusion lumen and
associated connectors, the pressure within the self-filling balloon
is less than the system pressure at the cardioplegic solution
source. If the cardioplegic solution contains blood, then care
should be taken to maintain the fluid pressure within the entire
cardioplegia system below approximately 300 mm Hg. It has been
found that blood subjected to pressures exceeding about 300 mm Hg
is subject to hemolysis.
The cardioplegic solution flow rate should be adjusted to maintain
a safe pressure within the coronary sinus, within the inner chamber
of the self-filling balloon, and throughout the cardioplegia
system. The flow rate is preferably maximized within the above
constraints.
Under anticipated operating conditions, the flow rate of
cardioplegic solution will be preferably in the range from about
200 ml/min to about 300 ml/min. The flow rate may vary depending
upon the extent of coronary obstructions within the patient's heart
and upon other heart conditions such as heart temperature and
muscular tone of the coronary circulatory system.
Because the catheter is positioned within the coronary sinus during
the entire surgical procedure, additional cardioplegic solution may
be readily administered as needed. There is no need to repeatedly
insert the catheter within the coronary sinus or to hand hold the
catheter during infusion. Thus, the present invention facilitates
periodic infusion and its associated benefits. Periodic infusion is
necessary because all hearts receive some noncoronary collateral
blood flow which tends to wash away the cardioplegic solution.
Periodic infusion of cardioplegic solution at about twenty to
thirty minute intervals counteracts noncoronary collateral
washout.
During lengthy cardiac surgery, periodic infusion of the
cardioplegic solution provides a number of significant benefits.
For example, periodic infusion (1) maintains arrest, (2) restores
desired levels of hypothermia, (3) buffers acidosis, (4) washes
acid metabolites away which inhibit continued anaerobiosis, (5)
replenishes high-energy phosphates if the cardioplegia solution is
oxygenated, (6) restores substrates depleted during ischemia, and
(7) counteracts edema. Buckberg, "Strategies and Logic of
Cardioplegic Delivery" at 131.
The present invention is particularly useful in delivering
retrograde venous cardioplegia in combination with antegrade
cardioplegia. A combination of retrograde and antegrade
cardioplegia provides more homogeneous distribution of the
cardioplegic solution to the right and left ventricles, stops the
heart faster, and leads to more complete regional recovery of the
jeopardized muscle and the global left and right ventricles than
use of antegrade cardioplegia alone.
FIG. 5 illustrates one method of delivering antegrade and
retrograde cardioplegia in combination. Antegrade catheter 58 is
inserted according to the techniques of the prior art. Retrograde
catheter 10 is inserted within the coronary sinus as described
above. The initial infusion is made antegrade to achieve the most
rapid arrest of the heart tissues supplied by unobstructed coronary
arteries. Aortic infusion line 60 is clamped with aortic clamp 62
immediately after antegrade cardioplegia has been administered.
Vent line 64 is then opened by releasing a vent clamp 66.
Retrograde clamp 68 is opened and retrograde cardioplegia is
delivered via the coronary sinus to accomplish arrest and
protection of regions supplied by constricted or occluded venous
return of retrograde cardioplegic solution that flows into the
right atrium through the thebesian channels. This protocol can be
repeated during the surgical procedure when necessary for periodic
infusion of cardioplegic solution.
C. Methods of Manufacturing the Self-filling Balloon
Unlike other balloons manufactured for use with balloon catheters,
the balloon of the present invention does not stretch significantly
past its original shape and size during use. Hence, the balloon of
the present invention is to be distinguished from the typical prior
art balloon catheters which are intended to inflate to several
times their original size. Therefore, the balloon of the present
invention is manufactured at approximately the size required for
proper use. The balloon of the present invention is formed on a
balloon mandrel having dimensions corresponding to the shape and
size of the balloon. One such mandrel is illustrated in FIG. 6.
Balloon mandrel 70 includes a mandrel tip 72 and a mandrel shank
74. Located between the mandrel tip and shank is balloon mold 76.
The diameter of the mandrel tip and shank is approximately the same
as the diameter of the s flexible cannula to which the balloon is
to be ultimately securely attached.
To form a balloon, the balloon mandrel is dipped into a polymer
solution which leaves a thin polymer coating on the mandrel
surface. After the polymer has cured, the balloon is removed by
peeling the thin coating off the mandrel.
The polymer should be capable of being placed in solution. However,
the viscosity of the polymer solution affects the quality of the
resulting balloon. If the viscosity is too high, then the balloon
is too thick around those portions of the mandrel removed last from
the solution. If the viscosity is too low, then the mandrel must be
repeatedly dipped into the polymer solution to form a balloon thick
enough for practical use. Such a thickness would be in the range
from about 0.003 inches to about 0.005 inches with the presently
preferred thickness being about 0.004 inches. The presently
preferred viscosity of the polymer solution is about that of light
honey.
The speed with which the mandrel is dipped into and removed from
the polymer solution also affects the quality of the resulting
balloon. If the mandrel is dipped too fast, then air bubbles are
entrained within the polymer solution. If the mandrel is removed
too fast, the polymer solution tends to drag on the mandrel surface
leaving streaks of uneven thickness on the balloon. Dipping and
removing the mandrel too slowly permits the polymer solution to
evaporate, altering the viscosity of the solution. The time to dip
the mandrel should be in the range from about 45 seconds to about
75 seconds, while the time to remove the mandrel should be in the
range from about 135 seconds to about 165 seconds. The presently
preferred time to dip the mandrel is about 60 seconds and the time
to remove the mandrel is about 150 seconds.
It will be appreciated that in order to remove the balloon from the
mandrel, the balloon portion formed around the mandrel shank must
stretch to the balloon's maximum diameter. Thus, the polymer used
to form the balloon must have excellent elongation properties,
preferably with a percent elongation greater than about 600%. In
addition, the shape of the balloon should not deform during its
removal from the balloon mandrel.
Because the balloon is designed for in vivo use, it should
preferably be constructed of a material which exhibits very low
thrombogenicity. It has been found that the balloon may be suitably
constructed of polyurethane. One preferred type of polyurethane is
medical-grade TECOFLEX polyurethane, manufactured by Thermedics
(Woburn, Massachusetts), which may be purchased in a solution form.
More detailed information regarding this product is set forth in
U.S. Pat. No. 4,447,590.
A quantity of polyurethane is preferably dissolved in
tetrahydrofuran to form a solution having a concentration in the
range from about 8% to about 9% polyurethane. This concentration
results in a solution viscosity such that the mandrel is dipped
into the solution three (3) times in order to achieve the desired
balloon thickness.
Despite its apparent advantages, polyurethane possesses a high
affinity for itself. Raw polyurethane tends to bind with raw
polyurethane. The untreated surfaces of a newly formed balloon tend
to bind together upon removal from the balloon mandrel, thereby
resulting in a wrinkled, useless polyurethane mass. Therefore, in
order to successfully construct balloons for use in the retrograde
cardioplegia catheter of the present art with polyurethane, the
balloon surfaces must be coated with a substance that will inhibit
the self-affinity of polyurethane.
Several coating techniques known in the prior art have been
considered and rejected as unsuitable. One such technique is to
coat the mandrel with a powder, such as talcum powder, before
dipping into the polyurethane solution. The resulting balloon
contained trace amounts of talcum powder within the inner chamber.
Because the balloon is self-filling, the risk of talcum powder
being introduced into a patient's blood supply is considered
unacceptable.
In another technique, the mandrel was coated with a thin layer of
silicone prior to dipping the mandrel into the polyurethane
solution. However, the resulting balloon s contained an uneven
layer of polyurethane. This is likewise considered
unacceptable.
Thus a principal problem in manufacturing the self- filling balloon
within the scope of the present invention is to coat the inner
surface of the balloon after the balloon had been formed, but
before removal from the mandrel.
This problem is solved according to the present invention by
injecting a coating agent through a borehole in the center of the
mandrel such that the coating agent exits the mandrel at the
juncture between mandrel tip 72 and balloon mold 76. The coating
agent proceeds back along the surface of the balloon mold towards
the mandrel shank until the entire inner surface of the balloon is
coated.
As illustrated in FIG. 6, there is a hollow bore 78 through the
center of the balloon mandrel. The mandrel tip, which is threadably
attached to the balloon mold, also possesses a corresponding hollow
bore which opens into two exit holes 80.
Referring now to FIG. 7, to release a balloon 82 formed around the
periphery of the balloon mold, a coating agent 84 is injected
through the hollow bore, through the exit holes, and out the
juncture between the mandrel tip and balloon mold. The coating
agent separates the balloon from the mandrel as it proceeds along
the surface of the balloon mold.
One suitable coating agent is a solution silicone dissolved in
freon having a concentration of silicone in the range from about 3%
to about 10%. In one presently preferred embodiment, the silicone
concentration in freon is about 5%. The freon rapidly evaporates
leaving a thin film of silicone. The silicone also facilitates
removal of the balloon by lubricating the mandrel. The same
silicone/freon solution is preferably applied to the outer surface
of the balloon to prevent self adhesion of the polyurethane.
FIG. 8 illustrates a balloon which has been removed from the
mandrel and prepared for attachment to the cannula. In order to
prepare the balloon for attachment to the cannula, the portions of
the balloon formed around the mandrel tip and shank are cut leaving
two sleeves 86, preferably about one eighth (1/8) inch long,
extending from each end of the balloon. The sleeves are then
preferably solvent bonded to the flexible cannula. As mentioned
above, Tetrahydrofuran is the solvent of choice.
From the foregoing, it will be appreciated that the present
invention provides apparatus and methods for performing retrograde
cardioplegia which are simple and effective so that the advantages
of retrograde cardioplegia can be readily utilized by surgeons.
Additionally, it will be appreciated that the present invention
further provides apparatus and method for performing retrograde
cardioplegia which do not require right atrial isolation, right
atriotomy, and repeated cannulation of the apparatus.
Likewise, it will be appreciated that because the present invention
provides a retrograde cardioplegia catheter which can be quickly
and accurately inserted within the coronary sinus, the patient
suffers relatively little trauma.
It will also be appreciated that the present invention provides
apparatus and methods for performing retrograde cardioplegia which
allow surgeons to safely use the life-saving internal mammary graft
without making the surgical procedure cumbersome.
Finally, it will be appreciated that the present invention provides
a method for manufacturing a self-filling balloon adapted for use
with a retrograde cardioplegia catheter which can be safely and
efficiently coated with an agent for preventing self adhesion.
The present invention may be embodied in other specific forms
without departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
* * * * *